Re: Workqueues in Ada

[Wiktor Moskwa <wiktorDOTmoskwa@gmail.com>]

On 28.07.2007, Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> wrote:
> I thought Ada.Containers.Doubly_Linked_Lists can move elements between
> lists without copying. Have you checked that?

I think the problem is that each time a task takes a unit from the queue
Delete is called and just after it Append - without a custom storage
pool malloc and free are called very often.

> You could also try an alternative implementation of doubly-linked lists and
> webs:
>
> http://www.dmitry-kazakov.de/ada/components.htm#Generic_Doubly_Linked_Web

It looks promising, especially with an ability to pass a storage pool
as a generic parameter. I'll check it out.

> Make it a protected object. A worker task calls to an entry of, requesting
> an item of work. The entry removes the first item from the list and returns
> it to the task via pointer. When the worker task finishes dealing with the
> item it calls to a protected object's procedure to queue the item back.

That's how it works now - I forgot to mention that my list is wrapped in 
a protected object, otherwise it wouldn't work :)
My idea of using a circular list is to call Delete and Append only when
new node joins the system or an old one leaves. During normal operations
a task will request new unit of work without deleting it from the queue.
It will be only marked as "currently in use". Other tasks will skip
this node - Next_To_Service pointer will move clockwise skipping nodes
that are serviced at the moment.

Thanks for your reply Dmitry.

-- 
Wiktor Moskwa